- <title>Configuration Format</title>
-
- <para>The configuration files should simply contain a
- list of variable assignments, separated by
- newlines. Empty lines and lines whose first
- non-whitespace character is # or ; are ignored.</para>
-
- <para>Note that both / and . are accepted as
- separators in sysctl variable names.</para>
+ <title>Configuration Format</title>
+
+ <para>The configuration files contain a list of
+ variable assignments, separated by newlines. Empty
+ lines and lines whose first non-whitespace character
+ is <literal>#</literal> or <literal>;</literal> are
+ ignored.</para>
+
+ <para>Each configuration file shall be named in the
+ style of <filename><replaceable>program</replaceable>.conf</filename>.
+ Files in <filename>/etc/</filename> override files
+ with the same name in <filename>/usr/lib/</filename>
+ and <filename>/run/</filename>. Files in
+ <filename>/run/</filename> override files with the same
+ name in <filename>/usr/lib/</filename>. Packages
+ should install their configuration files in
+ <filename>/usr/lib/</filename>. Files in
+ <filename>/etc/</filename> are reserved for the local
+ administrator, who may use this logic to override the
+ configuration files installed by vendor packages. All
+ configuration files are sorted by their filename in
+ lexicographic order, regardless of which of the
+ directories they reside in. If multiple files specify the
+ same variable name, the entry in the file with the
+ lexicographically latest name will be applied. It is
+ recommended to prefix all filenames with a two-digit
+ number and a dash, to simplify the ordering of the
+ files.</para>
+
+ <para>Note that either <literal>/</literal> or
+ <literal>.</literal> may be used as separators within
+ sysctl variable names. If the first separator is a
+ slash, remaining slashes and dots are left intact. If
+ the first separator is a dot, dots and slashes are
+ interchanged. <literal>kernel.domainname=foo</literal>
+ and <literal>kernel/domainname=foo</literal> are
+ equivalent and will cause <literal>foo</literal> to
+ be written to
+ <filename>/proc/sys/kernel/domainname</filename>.
+ Either
+ <literal>net.ipv4.conf.enp3s0/200.forwarding</literal>
+ or
+ <literal>net/ipv4/conf/enp3s0.200/forwarding</literal>
+ may be used to refer to
+ <filename>/proc/sys/net/ipv4/conf/enp3s0.200/forwarding</filename>.
+ </para>